Involvement of dopamine D2 receptors in complex maze learning and acetylcholine release in ventral hippocampus of rats

In the current study we focus on the involvement of dopamine D-2 receptors in the ventral hippocampus in memory performance and acetylcholine release. Using the aversively motivated 14-unit T-maze (Stone maze) the injection of raclopride, a D-2 receptor antagonist. into the ventral hippocampus (8 mug/kg) was found to impair memory performance. Co-injection of quinpirole, a D-2 receptor agonist (8 mug/kg), overcame the impairment in performance. Microdialysis study revealed that quinpirole infusion (10-500 muM) into the ventral hippocampus stimulated acetylcholine release in a dose-dependent manner, and systemic injection of quinpirole (0.5 mg/kg, i.p.) also stimulated acetylcholine release in the ventral hippocampus. Infusion of eticlopride, another D-2 receptor antagonist, into the ventral hippocampus suppressed acetylcholine release in the hippocampus induced by systemic injection of quinpirole. Taken together, we suggest that D-2 receptors in the ventral hippocampus are involved in memory performance, possibly through the regulation of acetylcholine. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.